I'd go .015 and .020 and see how it checks hot, and, you don't necessarily have to make a run to see what "hot" settings are. You can use the fan switch to run the engine temp up around 200/210 degrees and let it run there for a few minutes and you should be in the ball park to check it hot. Might even run it up on the verter a couple of times to put heat in it quicker. And you can do all this at home.

A little on the tight side is better than too loose, IMHO as when it's tight it's just picking up the ramp earlier whereas when it's loose it's late on the ramp and that jars the lifter more.

If memory serves, that 496 of gdmii's was .004 off as well cold to hot.